1. Field of the Invention
The present invention relates to a syringe and a syringe assembly having such an arrangement that a medical fluid held in a barrel is expelled from the barrel via a fluid expelling passage of the barrel, as well as an apparatus for manufacturing the same.
2. Discussion of the Background
Generally, a syringe assembly includes:
a tubular barrel having an open proximal end through which a medical fluid is introduced into the barrel, and a distal end with a fluid expelling passage through which the medical fluid held in the barrel is expelled into the body of a person to be treated;
an elastic seal disposed within a barrel chamber in fluid-tight and axially-sliding engagement with the inner wall of the chamber; and
a plunger rod having a proximal end projecting proximally from the proximal end of the barrel, and a distal end interconnected to the seal, so that the medical fluid held in the barrel chamber is expelled from the barrel chamber via the fluid expelling passage by sliding the seal by using the plunger rod.
In the above arrangement, it is necessary to slide the seal within the barrel chamber as maintaining the seal in fluid-tight engagement with the inner wall of the barrel chamber. To achieve high slidability of the seal relative to the inner wall of the barrel chamber, a conventional syringe assembly employs lubricant such as a silicon oil, which is applied to the entire surface of the inner wall of the barrel chamber so as to form a silicon film.
Although the silicon oil is not harmful even if it is introduced into the body, it is preferable to limit the quantity of the silicone oil introduced into the body. However, the conventional syringe of the above arrangement causes the medical fluid filled in the barrel chamber to constantly contact the silicon film, resulting in a high possibility of elusion of silicon into the medical fluid. Particularly, a pre-filled syringe assembly, which is shipped with the medical fluid therein, causes the medical fluid to contact the silicon film for a prolonged period of time, resulting in increasing the possibility of the elusion of silicon. Further, unlike a barrel formed from glass, a barrel formed from plastic may increase the possibility of the elusion of the silicon into the medical fluid, since silicone cannot be baked on the plastic barrel.
Therefore, the present invention has been conceived to solve the above problems in a syringe of the type that includes the tubular barrel, the seal held within the barrel chamber in fluid-tight and axially sliding engagement with the inner wall of the barrel chamber of the barrel, so that a fluid held in the chamber is expelled from the barrel chamber by sliding the seal. It is an object of the present invention to provide a syringe and a syringe assembly capable of preventing lubricant from being introduced into a fluid or a fluid forming drug held in the barrel chamber, as maintaining the seal in fluid-tight and sliding engagement with the inner wall of the barrel chamber.
It is another object of the invention to provide an apparatus for manufacturing the syringe and the syringe assembly of the above arrangement.
In accordance with the present invention, there. is provided a syringe including a barrel and a seal being forced into a barrel chamber of the barrel, the seal defining at least two diametrically enlarged portions at axially spaced apart portions of the seal so as to be respectively in abutment with the inner wall of the barrel and a concave portion between adjacent diametrically enlarged portions of the at least two diametrically enlarged portions for defining a clearance relative to the inner wall of the barrel chamber, in which (1) lubricant does not exist on the inner wall of the barrel chamber of the barrel with the exception of the portion of the inner wall at which the seal is held, (2) lubricant film exists only at interfaces between the at least two diametrically enlarged portions of the seal and the inner wall of the barrel chamber, and (3) lubricant is filled in the clearance between the inner wall of the barrel chamber and the concave portion. This arrangement can effectively prevent fluid held in the barrel from contacting lubricant, thereby maintaining fluid-tight characteristic and slidability of the seal and simultaneously preventing the mixture of the lubricant into the fluid.
It may be preferable to employ the arrangement where the lubricant film does not exist at an interface between the inner wall of the barrel and one diametrically enlarged portion that is distally positioned among the at least two diametrically enlarged portions of the seal. Thereby, the mixture of the lubricant into the fluid can more effectively be prevented.
It may be possible to provide a syringe assembly by equipping the syringe with a plunger rod having a proximal end projecting proximally from the proximal end of the barrel, and a distal end interconnected to the seal.
When used in a pre-filled syringe assembly, the syringe of the present invention produces a more remarkable effect as compared with the conventional syringe.
The apparatus of the present invention is configured so that a projecting portion of a lubricant applying unit is plunged into the barrel chamber of the syringe, and under this state, the seal having the diametrically enlarged portions onto which the lubricant is applied and the concave portion into which lubricant is filled can be forced into the barrel chamber. Thereby, it is possible to effectively manufacture the syringe having the arrangement where the lubricant film exists only at the interfaces between the inner wall of the barrel chamber and the diametrically enlarged portions of the seal, and the lubricant is filled in the clearance.